Improvement of water resistance of wheat flour-based adhesives by thermal-chemical treatment and chemical crosslinking

A water-resistant adhesive for plywood panels for engineered wood floors was developed using thermal-chemically treated wheat flour (WF), polyvinyl alcohol (PVA), and polymeric diphenylmethane diisocyanate (p-MDI) as the cross-linker. The thermal-chemical treatment was performed at 100 degrees C in the presence of sulfuric acid or sodium dodecyl sulfate (SDS). Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and scanning electron microscopy were used to investigate the chemical structure, crystalline degree, and morphology change, respectively, of the thermal-chemically treated WF. The boiling water-insoluble content and acetaldehyde values of the thermal-chemically treated WF were also evaluated and compared with those of the controls-native WF and thermally treated WF alone. The bond property evaluation showed that the water resistance of the thermal-SDS-treated WF (T-SDS-WF)-based adhesive was significantly improved, which is mainly attributed to the formation of a three-dimensional crosslinking network resulting from self-crosslinking of the wheat protein, the Maillard reaction between the wheat starch and wheat protein, and the increased crosslinking between T-SDS-WF and p-MDI. Overall, the developed WF-based adhesive is a promising bio-based candidate in the production of plywood for engineered wood floors.

Automated summary

A water-resistant adhesive for plywood panels for engineered wood floors was developed using thermal-chemically treated wheat flour, polyvinyl alcohol, and polymeric diphenylmethane diisocyanate as the cross-linker. Studies showed that the water resistance of the thermal-SDS-treated WF-based adhesive was significantly improved, mainly attributed to the formation of a three-dimensional crosslinking network, Maillard reaction, and increased crosslinking.